Many sheet-form products are economically produced in large volume by continuous molding or calendaring of plastic resins. In the touch fastener industry, molded plastic hook tape has displaced traditional woven fabric fasteners for many applications, simply because of lower production costs. However, molded, rolled or extruded resin fastener tapes are generally found to be more susceptible to tearing than are fastener tapes with woven or knit ground fabrics, particularly when notched such as by sewing the fastener tape to an underlying garment or other product.
Furthermore, the chain-like molecules of the resin forming the strip-form bases of products manufactured in continuous lengths can be found to become somewhat oriented toward the machine, or processing, direction by elongation or drawing of the material while still somewhat molten, further reducing the ability of the final product to resist tears propagating along the length of the tape.
Unfortunately, for many applications the fastener tape is ultimately sewn in place with at least one row of stitches extending along the length of the tape, forming a closely-spaced row of punctures or perforations extending along a direction most susceptible to tearing. It is along this weakened perforation line that load is transferred from the closure to the underlying substrate, through the thread passing through the punctures. Tears frequently result, extending along the stitch line and separating the fastener component from the rest of the product. This tearing may be readily evident, or result in a premature failure in use.
Various improvements have been suggested for increasing the longitudinal tear resistance of molded hook fastener tape. For example, surface features have been molded onto the surface of the base of the tape, between adjacent fastener elements, to help to impede tears propagating along the tape between rows of fastener elements. Strings, screens, yarns, paper and other materials have been laminated to, or embedded in, resin fastener tape bases. Resins of improved material properties have been considered, although for many applications the base resin is the same resin from which the fastener elements are formed, and so resin properties must be selected for fastener element formation and function as well as base tear resistance.
Further improvements in reinforcing plastic fastener tape, and other sheet-form or strip-form resin products, are desired, particularly for increasing tear resistance. Preferably, such improvements can be obtained without substantial increase in overall thickness, stiffness or cost of the final product.